1. Field of the Invention
The present invention relates to a gas separation apparatus, and more particularly, to a gas separation apparatus based on a vacuum swing absorption (VSA) method.
2. Description of the Conventional Art
Generally, a gas separation apparatus is for separating nitrogen and oxygen that are main components of the air from each other, and is used for domestic or industrial use.
The gas separation apparatus serves as both an oxygen generator and a nitrogen generator. As the oxygen generator, the gas separation apparatus is variously used for individual, domestic, automobile, emergency, industrial use, etc., and is recently used to increase a dissolved oxygen inside drinking water by being supplied to drinking water of a domestic water purifier. Also, as the nitrogen generator, the gas separation apparatus is used to generate nitrogen of a high purity for an industrial use, and is used to control a storage atmosphere for a long-term storage of food. The gas separation apparatus separates specific gas by sucking the air and thus transmitting the air to an adsorbent for absorbing specific gas or an enrichment membrane.
A method for sucking the air and thus transmitting to an absorbent or an enrichment membrane includes a pressure swing absorption (PSA) method for applying a pressure and generating a gas flow, and a vacuum swing absorption (VSA) method for lowering a pressure inside a conduit and generating an air flow using a pressure difference between the pressure inside the conduit and the air pressure.
As shown in FIG. 1, the conventional gas separation apparatus based on the VSA method comprises: first and second absorption beds 111 and 112 including an absorbent for absorbing specific gas; a vacuum pump 113 for forming a vacuum state inside the first and second absorption bends 111 and 112; a discharge pump 114 for discharging gas separated by the absorbent of the first and second absorption beds 111 and 112; a filter 115 for filtering external gas introduced into the first and second absorption beds 111 and 112; and first and second three-way valves 121 and 122 installed on a conduit that respectively connects the first and second absorption beds 111 and 112, the vacuum pump 113, and the filter 115, for selectively connecting the first and second absorption beds 111 and 112 to the vacuum pump 113, or selectively connecting the first and second absorption beds 111 and 112 to the filter 115, that is, the air.
Operation of the conventional gas separation apparatus based on the VSA method will be explained as follows.
First, a process for separating gas from the first absorption bed 111 and thereby discharging will be explained.
When the first absorption bed 111 and the vacuum pump 113 are connected to each other by an operation of the first three-way valve 121, the vacuum pump 113 is operated and thereby an inner pressure of the first absorption bed 111 is reduced thus to form a vacuum state. Also, when the first absorption bed 111 and the filter 115 (that is, outside of the gas separation apparatus) are connected to each other by the operation of the first three-way valve 121, a pressure difference between inside of the first absorption bed 111 and outside of the gas separation apparatus is generated. According to this, gas that has passed through the filter 115 is introduced into the first absorption bed 111. Among the gas introduced into the first absorption bed 111, certain gas is absorbed by the absorbent, and gas that has not been absorbed by the absorbent is discharged to outside of the gas separation apparatus by the operation of the discharge pump 114.
When the first absorption bed 111 and the vacuum pump 113 are connected to each other by an operation of the first three-way valve 121, gas that has been absorbed by the absorbent in the first absorption bed 111 is detached from the absorbent by a suction force of the vacuum pump 113. The gas detached from the absorbent passes through the vacuum pump 113 thus to be discharged to outside of the gas separation apparatus. At the same time, inside of the first absorption bed 111 is again in a vacuum state.
A process for separating gas from the second absorption bed 112 is the same as the process for separating gas from the first absorption bed 111. If operation periods of the first and second three-way valves 121 and 122 are alternately set, a discharge of separated gas by the vacuum pump 113 and the discharge pump 114 is consecutively performed. That is, when the vacuum pump 113 and the first absorption bed 111 are connected to each other by the first three-way valve 121, the filter 115 and the second absorption bed 112 are connected to each other by the second three-way valve 122. Also, when the filter 115 and the first absorption bed 111 are connected to each other by the first three-way valve 121, the vacuum pump 113 and the second absorption bed 112 are connected to each other by the second three-way valve 122.
Said operation is repeatedly performed, and gas that has not been absorbed by the absorbent in the first and second absorption beds 111 and 112 is discharged out through the discharge pump 114. Also, gas absorbed by the absorbent is discharged through the vacuum pump 113. Under this operation, when the absorbent has a characteristic to be absorbed with nitrogen, oxygen among the air introduced into the gas separation apparatus is discharged through the discharge pump 114, and nitrogen is discharged through the vacuum pump 113.
However, in the conventional gas separation apparatus based on the VSA method, the vacuum pump 113 for discharging gas absorbed by the absorbent and the discharge pump 114 for discharging gas that is not absorbed by the absorbent have to be all provided thus to have a high cost and have a complicated construction.